“Hypersensitive reaction” (HR) is a known plant resistance response against the invasion of pathogens such as pathogenic microorganisms and pests. Specifically, when a pathogen invades, plants attempt to defend themselves by rapidly causing the death of infected cells using the HR-mediated loss of cellular turgor pressure. Cell groups killed by the reaction necrotize, become brown, and form local lesions to prevent pathogen expansion. Thus, enhancing plant HR is thought to be important when breeding pathogen-resistant plants.
Lesion mimic mutants that form necrotic spots even in the absence of pathogen invasion are known to exist. Some of these mutants are plants whose resistance mechanism is constantly activated. These lesion mimic mutants include rice cdr1 to cdr3 and sp11 to sp19 (see Non-patent Documents 1 and 2).
Genes that cause spotted leaves are also thought to include genes that induce HR; however, only a few HR-inducing genes have actually been isolated. In rice, only Rac and G protein alpha subunit are known as such HR-inducing genes (see Non-patent Documents 3 and 4).
Transcription of many genes is known to be activated during HR in tobacco (see Non-patent Documents 5 to 10). Nicotiana tabacum hsr201 is reported as one such gene, and its transcription is induced by HR (Non-patent Document 6), but it is not known whether overexpression of the gene induces HR.
Non-patent Document 1: Takahashi A, Tsutomu Kawasaki, Kenji Henmi, Katsuhiko Shii, Osamu Kodama, Hikaru Satoh, Ko Shimamoto. Lesion mimic mutants of rice with alterations in early signaling events of defense. Plant J (1999) 17(5):535-545.
Non-patent Document 2: Yin Z, Chen J, Zeng L, Goh M, Leung H, Khush G S, Wang G L. Characterizing rice lesion mimic mutants and identifying a mutant with broad-spectrum resistance to rice blast and bacterial blight. Mol Plant Microbe Interact. 2000 Aug.; 13(8):869-76.
Non-patent Documents 3: Ono E, Wong H L, Kawasaki T, Hasegawa M, Kodama O, Shimamoto K. Essential role of the small GTPase Rac in disease resistance of rice. Proc Natl Acad Sci USA. 2001 Jan. 16; 98(2):759-64.
Non-patent Document 4: Suharsono U, Fujisawa Y, Kawasaki T, Iwasaki Y, Satoh H, Shimamoto K. The heterotrimeric G protein alpha subunit acts upstream of the small GTPase Rac in disease resistance of rice. Proc Natl Acad Sci USA. 2002 Oct. 1; 99(20):13307-12.
Non-patent Document 5: Pellegrini L, Rohfritsch O, Fritig B, Legrand M. Phenylalanine ammonia-lyase in tobacco. Molecular cloning and gene expression during the hypersensitive reaction to tobacco mosaic virus and the response to a fungal elicitor. Plant Physiol. 1994 November; 106(3):877-86.
Non-patent Document 6: Czemic P Huang H C, Marco Y. Characterization of hsr201 and hsr515, two tobacco genes preferentially expressed during the hypersensitive reaction provoked by phytopathogenic bacteria. Plant Mol Biol. 1996 May; 31(2):255-65.
Non-patent Document 7: Hiraga S, Ito H, Yamakawa H, Ohtsubo N, Seo S, Mitsuhara I, Matsui H, Honma M, Ohashi Y. An HR-induced tobacco peroxidase gene is responsive to spermine, but not to salicylate, methyl jasmonate, and ethephon. Mol Plant Microbe Interact. 2000 February; 13(2):210-6.
Non-patent Document 8: Dhondt S, Geoffroy P, Stelmach B A, Legrand M, Heitz T. Soluble phospholipase A2 activity is induced before oxylipin accumulation in tobacco mosaic virus-infected tobacco leaves and is contributed by patatin-like enzymes. Plant J. 2000 August; 23(4):431-40.
Non-patent Document 9: Yoda H, Ogawa M, Yamaguchi Y, Koizumi N, Kusano T, Sano H. Identification of early-responsive genes associated with the hypersensitive response to tobacco mosaic virus and characterization of a WRKY-type transcription factor in tobacco plants. Mol Genet Genomics. 2002 April; 267(2):154-61.
Non-patent Document 10: Sasabe M, Toyoda K, Shiraishi T, Inagaki Y, Ichinose Y. cDNA cloning and characterization of tobacco ABC transporter: NtPDR1 is a novel elicitor-responsive gene. FEBS Lett. 2002 May 8; 518(1-3):164-8.